Left Circumflex Coronary Artery Hemodynamics in Conscious Dogs with Congenital Subaortic Stenosis

Coronary arterial hemodynamics were studied in three conscious dogs with congenital fibrous ring-type subaortic stenosis. Flow characteristics were recorded with electromagnetic flow transducers chronically implanted on the circumflex branch of the left coronary artery. Circumflex resting flow (ml/min 100 g myocardium) was below that previously found in normal dogs studied by the same methods. Phasic coronary flow patterns at rest were abnormal, being characterized by reversed flow throughout most of ventricular systole. The mean reactive hyperemic response after 10 seconds of mechanical occlusion was comparable to that in normal dogs despite the essential absence of systolic forward flow. In one dog, moderate treadmill exercise substantially increased total circumflex flow despite a large increase in reversed circumflex flow.